31x10.50R15 vs 33x12.50R15: full comparison
| Measurement | 31x10.50R15 | 33x12.50R15 | Difference |
|---|---|---|---|
| Diameter | 31.00 in | 33.00 in | +2.00 in+6.5% |
| Section width | 10.50 in | 12.50 in | +2.00 in+19.0% |
| Sidewall height | 8.00 in | 9.00 in | +1.00 in+12.5% |
| Circumference | 97.39 in | 103.67 in | +6.28 in+6.5% |
| Revs per mile | 651 | 611 | −39−6.1% |
Speedometer: indicated vs actual speed
With 33x12.50R15 fitted where 31x10.50R15 was the stock/calibrated size:
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 21.3 mph | +1.3 mph |
| 30 mph | 31.9 mph | +1.9 mph |
| 40 mph | 42.6 mph | +2.6 mph |
| 50 mph | 53.2 mph | +3.2 mph |
| 55 mph | 58.5 mph | +3.5 mph |
| 60 mph | 63.9 mph | +3.9 mph |
| 65 mph | 69.2 mph | +4.2 mph |
| 70 mph | 74.5 mph | +4.5 mph |
| 75 mph | 79.8 mph | +4.8 mph |
| 80 mph | 85.2 mph | +5.2 mph |
Recalculate for a gear ratio change too →
Will 33x12.50R15 fit where 31x10.50R15 was?
At +6.5%, 33x12.50R15 is enough larger than 31x10.50R15 that it commonly needs some accommodation -- trimming plastic liners/fender edges, a spacer, or a leveling kit on trucks/SUVs going bigger. Check clearance at full steering lock and full suspension compression before buying.
More tire tools
- Tire size comparison tool: compare any two sizes yourself, including flotation sizes.
- Tire size calculator: full dimensions of one size, plus every equivalent size within 3%.
- Speedometer calculator: true speed after a tire or gear ratio change.
Frequently asked questions
How much bigger is 33x12.50R15 than 31x10.50R15?
33x12.50R15 is 2.00 in taller in overall diameter (+6.5%) and 2.00 in wider in section width (+19.0%) than 31x10.50R15.
Will 33x12.50R15 fit in place of 31x10.50R15?
At +6.5%, 33x12.50R15 is enough larger than 31x10.50R15 that it commonly needs some accommodation -- trimming plastic liners/fender edges, a spacer, or a leveling kit on trucks/SUVs going bigger. Check clearance at full steering lock and full suspension compression before buying.
Does swapping to 33x12.50R15 affect my speedometer?
With 33x12.50R15 fitted where 31x10.50R15 was calibrated, an indicated 60 mph is really about 63.9 mph. Beyond the ±3% guideline, plan to recalibrate the speedometer/odometer (with a programmer or at the dealer) for an accurate reading.
Does 33x12.50R15 change the ride height?
Yes -- half the diameter difference shows up at the axle, so 33x12.50R15 changes ride height by about 1.00 in higher compared with 31x10.50R15.
Do 31x10.50R15 and 33x12.50R15 use the same wheel (rim) diameter?
Yes -- both fit a 15 inch wheel, so only the tire itself changes, not the wheel.